Further more, you get errors when running "sudo apt-get update", the Update Manager refuses to upgrade packages and so on.

Do you remember Launchpad-Getkeys - a script that automatically imports all missing GPG keys? Well, if you're behind a firewall, you'll be glad to know that Launchpad-Getkeys now works on port 80 by default so it should finally fix the missing GPG keys issue. I've completely rewritten the script (which was initially posted by blackgr @ ubuntuforums) to only imports the missing GPG keys (it used to import all the keys each time you ran it, even if you only had one missing key). In the new version I've also added an option to use a different keyserver (use: -k SERVER:PORT).

Install and use Launchpad-Getkeys

To install the package in Ubuntu Karmic, Lucid, Maverick and Natty, use the following commands: